1. Field of the Invention
This invention relates to a device for detecting a reference position of a magnetic head, and more particularly to a device for detecting a reference position of a magnetic head to perform magnetic recording or reproduction on a cassette type magnetic disc while moving in the radial direction of the magnetic disc.
2. Description of the Prior Art
Recently, there has been developed an electronic camera system wherein an image pickup device, such as a solid state image sensing device or ,an image pickup tube, is combined with a recording device using an inexpensive magnetic disc as a recording medium and having a comparatively high memory capacity. A subject is still-photographed electronically and recorded onto a rotating magnetic disc. The reproduction of an image is carried out by a television system, a printer or the like, which are provided separately.
In an image recording or reproducing system using such a magnetic disc as described above, there is used the disc having a diameter of about 50 mm. Furthermore, in this magnetic disc, there is formed a recording pattern from track 1 to track 52 from the outer peripheral side toward the inner peripheral side. The magnetic head feed is about 100 .mu.m, which is substantially smaller than the feed pitch of an ordinary floppy disc, so that the magnetic head should be moved with very high accuracy. A home position serving as a starting position (move starting position) of the magnetic head is provided at a predetermined position located at the outer peripheral side from the track 1 within the track 1 and functions as a reference position when the magnetic head is transferred in the radial direction of the magnetic disc for recording or reproducing. An end position serving as a tail end position (ending position) of the magnetic head is provided at a predetermined position located at the inner peripheral side from the track 52 and functions such that the magnetic head does not move over a predetermined recording range of the magnetic disc. Accordingly, in the magnetic disc device of the electronic camera system, it is necessary that the home position and the end position be detected so that the feed of the magnetic head may be stopped at the home position or the end position.
Further, when the magnetic head is fed at a constant value to perform recording onto the magnetic disc, the home position functions as a reference position for forming the respective tracks, so that the detection of the home position should be performed with high accuracy and the magnetic head should be stopped with high accuracy.
As a device for detecting the reference position of the type described, there have heretofore been used a leaf switch operable by a head carriage for moving the magnetic head when the magnetic head reaches the aforesaid reference position, and a device, wherein rotation of a stepping motor to drive the magnetic head is reduced, transmitted to a disc having a photoslit which is detected by a photointerruptor.
However, these devices are low in speed to a considerable extent, whereby the position detecting accuracy is low, so that these devices cannot be applied solely as means for detecting the reference position of the magnetic head.